Install OpenLDAP

This part is easy:

pacman -S openldap

The openldap package basically contains two things: The LDAP server (slapd) and the LDAP client. You will probably want to run the server on your computer. After you design the directory, the server will be able to provide authentication services for LDAP clients. It is quite likely that you will run services requiring the LDAP authentication on that very computer, in which case the LDAP client will query the LDAP server from the same package.

Configure OpenLDAP

The server (slapd)

First prepare the database directory. You will need to copy the default config file and set the proper ownership.

WARNING!!! - The following snippet wipes out any existing ldap database.

/etc/openldap/slapd.conf

Add some typically used schemas...

include /etc/openldap/schema/cosine.schema
include /etc/openldap/schema/nis.schema
include /etc/openldap/schema/inetorgperson.schema

Edit the suffix. Typically this is your domain name but it does not have to be. It depends on how you use your directory. We will use 'example' for the domain name, and 'com' for the tld. Also set your ldap administrators name (we'll use 'root' here)

suffix "dc=example,dc=com"
rootdn "cn=root,dc=example,dc=com"

Now we delete the default root password and create a strong one:

#find the line with rootpw and delete it
sed -i "/rootpw/ d" slapd.conf
#add a line which includes the hashed password output from slappasswd
echo "rootpw $(slappasswd)" >> slapd.conf

ldap won't find things unless you index them. Read the ldap documentation for details, you can use the following to start with. (add them to your slapd.conf)

It might be possible that /run/openldap does not exist, starting the daemon won't work. Just create the directory:

mkdir /run/openldap

/etc/conf.d/slapd

Very important, you define here on which port the server should listen and if you want to use SSL, you will want to use the ldaps:// URI instead of the default ldap://
You can also specify additional slapd options here.

The client

The client is usually not such a big deal, just keep in mind that your apps that require LDAP auth use it, so if something goes wrong with LDAP, do not waste your time with the app, start debugging the client instead.

The client config file is located at /etc/openldap/ldap.conf
It is actually very simple.

If you decide to use SSL:

The protocol (ldap or ldaps) in the URI entry has to conform with the slapd configuration

If you decide to use self-signed certificates, you have to add them to TLS_CACERT

Test your new OpenLDAP installation

This is easy, just run the command below:

ldapsearch -x -b -s base '(objectclass=*)' namingContexts

you should see some information on your database.

Next Steps

You now have a basic ldap installation. The step is to design your directory. The design is heavily dependent on what you are using it for. If you are new to ldap, consider starting with a directory design recommended by the specific client services that will use the directory (PAM, Postfix, etc).